There's a riveting and dark new documentary that digs into the life of one Vivian Maier, who took thousands of unbelievable street photos that didn't see the light of day until her death.

"Finding Vivian Maier" pays homage to her stunning work, but it also suggests Maier had a dark, sadistic side.

Maier — a poor child of a French mother who wore baggy clothes and floppy hats — worked as a nanny for a number of families in the Chicago area from the '50s to '90s. She was an odd woman. Maier always had a Rolleiflex camera around her neck and dragged her charges around Chicago's seedy areas to take pictures.

Those pictures often captured the weakest moments of their subjects, who included children weeping and a young boy who had just been hit by a car. Maier took one of her charges, Inger Raymond, to a stockyard, where she exposed the young child to the slaughter of livestock.

Near the end of the movie, Raymond reluctantly talks about her former governess's alleged abuse. That abuse included force-feeding. Maier stuffed food into the little girl's mouth and choked her until she swallowed, according to Raymond. Her nanny also threw her around the room when she couldn't tie her shoes quickly enough, Raymond says.

Other former charges also hinted at her darkness. One said Maier abandoned her by herself on the street so she could take pictures, while another simply said she was mean. A woman who hired Maier said the nanny kept massive stacks of newspapers with gruesome headlines around the house and grew livid when she tried to remove them. Eventually, Maier and that family parted ways.

Despite Maier's odd and mean behavior, at least two of her former charges had some affection for her, as they put her up in an apartment near the end of her life. In her final years, Maier often sat in the park, mumbling in French, eating food directly from a can, and accepting old clothes from strangers.

She would have left little mark on the world, if a 26-year-old real estate agent named John Maloof hadn't bought a massive box of her negatives in 2007. These days her name is mentioned along with the likes of photo legends Robert Frank and Diane Arbus. The families she worked for agreed that she would not have liked the attention.